1. Field of the Invention
The present invention relates to an automotive alternator provided with a surge absorber for absorbing surges arising in a voltage regulator for adjusting the magnitude of an alternating voltage generated in a stator.
2. Description of the Related Art
FIG. 8 is a cross section of a conventional automotive alternator (hereinafter "alternator"); FIG. 9 is a front elevation of the interior of the alternator in FIG. 8, FIG. 10 is a view of the interior of the alternator in FIG. 8 from the direction of arrow A (Note: regulator is sectioned), FIG. 11 is a view a view of the interior of the alternator in FIG. 8 from the direction of arrow B, FIG. 12 is a cross section taken along line XII--XII in FIG. 11 (Note: surge absorber is not sectioned), and FIG. 13 is an exploded perspective of the surge absorber in FIG. 12.
This alternator includes: a case 3 consisting of an aluminum front bracket 1 and an aluminum rear bracket 2; a shaft 6 disposed in the case 3 to one end of which a pulley 4 is secured; a Lundell-type rotor 7 secured to the shaft 6; fans 5 secured to both end surfaces of the rotor 7; a stator 8 secured to the inner wall of the case 3; and slip rings 9 secured to the other end of the shaft 6 for supplying electric current to the rotor 7.
This alternator also includes: a base 100 having an inserted conductor embedded therein by insertion molding with PPS resin; a brush holder 11 integrated with the base 100 accommodating in a housing recess 11a a pair of brushes 10 moving in contact with the slip rings 9; a rectifier 12 electrically connected to the stator 8 for converting alternating current generated in the stator 8 into direct current; a voltage regulator 13 fitted into the brush holder 11 for adjusting the magnitude of the alternating current generated in the stator 8; an arc-shaped flow control plate 14 disposed opposite the fans 5 for directing air drawn into the case 3 by the rotation of the fans 5 to the voltage regulator 13; a surge absorber 15 integrated with the base 100 for absorbing surges generated as the voltage regulator 13 regulates the voltage; and a connector 16 integrated with the base 100.
The rotor 7 includes: a rotor coil 17 for generating magnetic flux when electric current passes therethrough; and a pole core 18 disposed so as to cover the rotor coil 17 in which magnetic poles are produced by the magnetic flux generated by the rotor coil 17.
The stator 8 includes: a stator core 19; and a stator coil 20 composed of wire wound onto the stator core 19 in which alternating current is generated by changes in the magnetic flux from the rotor coil 17 as the rotor 7 rotates.
The voltage regulator 13 is housed in a recessed housing portion 21 formed in the brush holder 11. The voltage regulator 13 includes: a circuit board 22; a voltage regulator circuit portion 23 having IC chips, etc., mounted on the circuit board 22; lead pins 24 electrically connecting the voltage regulator circuit portion 23 to the inserted conductor in the base 100; cooling fins 25 secured to the circuit board 22; and a resin portion 26 sealing the voltage regulator circuit portion 23.
As shown in FIGS. 12 and 13, the surge absorber 15 includes: a case 27; and a capacitor element 30 having a rectangular parallelepiped shape over all disposed inside the case 27 for preventing the propagation of noise to the vehicle's electrical systems such as audio systems, blower fans, etc., by absorbing surges generated as the voltage regulator 13 regulates the voltage. This surge absorber 15 is inserted into a receiving portion 32 formed in the base 100. The positive terminal 33 and the negative terminal 34 of the capacitor element 30 are secured by soldering to the terminals 35 of the inserted conductor in the base 100.
The connector 16 shown in FIGS. 14 and 15 includes terminal 36 for detecting battery voltage and terminal 36 for alerting the driver of the vehicle to overvoltage and inoperation of the alternator. These terminals 36 are constituted by the terminals of the inserted conductor. Because the connector 16 is constructed for the insertion of an external connector 37, the opening 39 thereof is formed with dimensions allowing clearance for the outside dimensions of the external connector 37. For that reason, a rear surface portion 38 for preventing air from being drawn through the opening 39 into the interior of the case 3 by the rotation of the fans 5 is formed on the rear side of the opening 39. A flat surface portion 40 is formed on the surface of the connector 16 opposite the fans 5. This flat surface portion 40 lies on the same plane as the flow control plate 14 which is disposed axially overlapping the base 100, and thus, air from the rotating fans 5 flows smoothly over the flat surface portion 40 and the flow control plate 14, reducing noise.
In an alternator of the above construction, a current is supplied by a battery (not shown) through the brushes 10 and slip rings 9 to the rotor coil 17, whereby magnetic flux is generated. At the same time, the pulley 4 is driven by the engine and the rotor 7 is rotated by the shaft 6, so that a rotating magnetic field is imparted to the stator coil 20 and electromotive force is generated in the stator coil 20. This alternating electromotive force passes through the rectifier 12 and is converted into direct current, the magnitude thereof is adjusted by the voltage regulator 13, and the battery is recharged.
In an alternator of the above construction, the surge absorber 15 for preventing the propagation of noise is secured to the base 100 by inserting it into a receiving portion 32 formed in the base 100 and soldering the positive terminal 33 and the negative terminal 34 of the capacitor element 30 to the terminals 35 of the inserted conductor. That is to say, because the surge absorber 15 is held by the terminals 33 and 34, the dynamic load acting on the surge absorber 15 due to vibrations from the engine, etc., is concentrated on the terminals 33 and 34, and one problem has been the risk of breakages at the terminals 33 and 34.
Because the terminals 33 and 34 are exposed to the exterior, other problem have been electrolytic corrosion of the metal positive terminal 33 due to wetting with salt water or the like, or breaking of the wires at the joints between the terminals 33 and 34 and the terminals 35 of the inserted conductor due to natural corrosion.
Because the joints between the terminals 35 of the inserted conductor and the terminals 33 and 34 of the capacitor element 30 are solder with the terminals 33 and 34 overlapping in surface contact with the terminals 35 in the axial direction, other problems have been that the soldering operation can only be performed from the direction of arrow C in FIG. 12, and that the joint strength has been unstable due to the irregular shape of the terminals 35, for example.